Pulsed Plasma Etch With Sample Bias For Micro-Loading
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Solution Overview
Problem
Plasma etch processes face limitations in etching semiconductor structures with variable spacing, leading to micro-loading issues where etch rates vary with pattern density, resulting in over-etching and detrimental undercutting of structures.
Innovation Solution
A pulsed plasma etch method with pulsed sample bias is employed, where a negative bias is applied during the ON state and zero bias during the OFF state of each duty cycle, to mitigate etch rate dependency on structure density and reduce micro-loading by controlling the formation and removal of etch by-products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a plasma etch process is used to etch semiconductor structures with variable spacing, then the etching capability is improved, but micro-loading effects cause etch rate variation with pattern density leading to over-etching and undercutting
Solution Approach 1:
The patent applies periodic pulsed plasma cycles with alternating high-power and low-power phases. During high-power phases, etching proceeds at high rate; during low-power phases, etching continues at reduced rate allowing etch by-products to desorb from sidewalls. This periodic action equalizes etch rates across different pattern densities, eliminating micro-loading effects and preventing over-etching and undercutting while maintaining high overall etching productivity.
2Reliability
If over-etch is applied to complete etching in high density regions, then the etching completeness is improved, but detrimental undercutting occurs in low density regions
Solution Approach 1:
The pulsed plasma process uses periodic high-power and low-power phases to alternately advance the etch front and allow by-product desorption. This ensures that etching proceeds uniformly across all regions simultaneously, achieving complete etching in high density regions without requiring excessive over-etch that would cause undercutting in low density regions.
Solution Approach 2:
The patent dynamically changes plasma power parameters between high and low states during the etching process. This parameter modulation controls the etch rate and by-product formation/desorption balance, enabling complete etching while preventing undercutting by adjusting the etching conditions in real-time based on the need to remove etch by-products from sidewalls.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures a consistent etch rate across all density regions, minimizing over-etching and undercutting, thereby improving the uniformity and quality of semiconductor structures.
Implementation Method 1
A pulsed plasma process with pulsed sample bias is employed
Implementation Method 2
A negative bias is applied to the sample during the ON state of each duty cycle
Data Source
AI summary
A pulsed plasma system with pulsed sample bias for etching semiconductor structures is described. In one embodiment, a portion of a sample is removed by applying a pulsed plasma process, wherein the pulsed plasma process comprises a plurality of duty cycles. A negative bias is applied to the sample during the ON state of each duty cycle, while a zero bias is applied to the sample during the OFF state of each duty cycle. In another embodiment, a first portion of a sample is removed by applying a continuous plasma process. The continuous plasma process is then terminated and a second portion of the sample is removed by applying a pulsed plasma process.